With the re-release of `It's a Wonderful Life', new audiences can appreciate this heart-warming morality tale

This week, the 50th birthday of Frank Capra's It's a Wonderful Life is celebrated with a theatrical re-release, offering many people their first chance to see the film on the big screen. A bittersweet story of small-town redemption, Capra's feel-good fantasy describes how despairing father James Stewart is saved from suicide by an angel called Clarence who shows Stewart what the world would have been like if he had never lived.

Although well known in Britain, the movie is nothing like the institution it is in the States, where Capra's slice of archetypal Americana has been deemed "a national treasure" by Congress. But it was not always so. On its initial release in 1946 It's a Wonderful Life did only "moderate" box office and might have sunk without trace had it not achieved a television renaissance. "Without that rebirth, who knows?" says the director's son, Frank Capra Jr. "Maybe it would have disappeared after a 6-month run."

Now a movie producer himself, Capra Jr remembers visiting the set when he was 12 years old. "My brother and sister and I didn't go on set very often because our mother didn't want us turning into Hollywood brats," he says. "But seeing that set really stuck in my memory. It was midsummer in Los Angeles and here was a town covered with snow - winter in July, it was remarkable. In fact, I think the snow was nominated for an Academy award, because it was a new kind of effect."

Sadly, like the film's nomination for best picture, Capra's for best director and Stewart's for best actor, the snow failed to win an Oscar. Which makes it all the more remarkable how the film's success has snowballed over the years. "TV channels initially started showing it because it was free," says Capra Jr. "But they quickly started getting requests from the public. Pretty soon every channel ran it every year. My father always used to laugh and say it was Clarence doing it."

Achieving the kind of public vindication every artist dreams of, it's not surprising Capra felt a guardian angel was looking after him. Still, even the director would later marvel at the mythic resonance his work achieved. "There's more to this picture than I put in it. There's more to the picture than was written in it. There's more to it than we thought we had, and it's the picture I waited all my life to make."

Capra began work on It's a Wonderful Life immediately after the Second World War. "He'd spent hours and hours in the editing suite making Why We Fight documentaries and I think that sharpened his skills," says Capra Jr. "He was really ready to make a big film." Lead actor James Stewart, however, was not. "Jimmy had a lot of serious misgivings about even coming back to acting after the war," explains Capra Jr. "He was very upset. It was as if acting was frivolous, didn't matter any more." Ironically, it was Stewart's movie nemesis, Lionel Barrymore, who coaxed the star back into feeling pride in performance. "His view on all of that was `I get, up every morning and I thank God I'm an actor, I have the ability to make people laugh, to make people cry, to entertain'," says Capra Jr.

Stewart later described his role in the film as the best of his career, while for many viewers it's their favourite movie of all time. So what is it exactly that makes it endure? Despite hundreds of viewings, Capra Jr has yet to get sick of watching the film. "It's not The Rocky Horror Picture Show yet," he laughs. "Because even if you know most of the lines you can't watch it without it affecting you, getting sucked in emotionally."

The producer's own favourite moment from the film is a shot of Jimmy Stewart fleeing in terror from "Pottersville", the den of iniquity his home town might have become without his presence. For Capra Jr the immoral and ugly Pottersville imagined by his father was "a prescient look at what many American towns have actually become". As powerful a reason as any for why modern audiences never tire of replaying Capra's life-affirming morality tale, of reassuring themselves that It's a Wonderful Life.

`It's A Wonderful Life' is on release. See New Films, p19